nuckolls.bob(at)aeroelect
Guest
|
 Posted: Tue Jan 27, 2015 6:52 am Post subject: Dual Alternator, Dual Battery, Single Bus |
 |
|
The below not withstanding, Dynon recommends starting and stopping
the engine with the /Skyview not connected to the ships buss. They
recommend starting the engine on the skyview backup battery so that
you can see the engine instruments and connecting to the ships power
after start. What do they know that we don't?
Rich
Keep in mind that we're talking about
two different classes of behavior for
a DC powered appliance:
The most critical being resistance to
environmental effects that cause transient
or even permanent loss of performance.
In the case of 1967 nav/com 300 radios,
the effect was blown power supply
transistors that were not protected against
a brown-out event. Vacuum tubes didn't give
a rip . . . who would have thought that
this new solid state thingy would be so
particular?
The other concern is for operational
availability. All of my designs are vulnerable
to brown-out events below some value of
bus voltage . . . but they come alive
milliseconds after the event. Other
systems are not so light on their feet.
Some years ago we marched through this
forest of thought when the Blue Mountain
products (based on MS Dos as I recall)
demonstrated recovery times of 60 or so
seconds to stand up after falling on the
ground. The system was not damaged by the low-
voltage event but it was temporarily
unavailable.
This is an area of appliance marketing
that many suppliers put their foot into the
tar bucket. A famous supplier who shall
remain nameless actually published a
full-up, two-battery, two-alternator,
split bus system in the back of their
installation manual . . . a 'suggestion'
that went far afield with respect to the
airplane's performance. I have some clients
who have asked me to help craft recommended
applications for their products . . .
requests that I have declined. The reason
is simple. Any supplier is obligated to
define the behavior of their product
in detail.
But refrain from uttering any imperatives
intended to mitigate some temporary loss
of performance event. The DATA says, "This
product may take xx seconds to reboot after
a brown-out event." They should stop right
there. It's up to the system integrator to
decide the operational significance of
that characteristic.
What does Dynon, et als know? Their
gizmo, like all others, will initiate a restart
cycle after a brown-out event. They should tell
you how long that is. They should also mention
that alternative sources of power can be
used to prevent the reboot . . . and stop
right there. But as soon as they venture
into operational imperatives or 'recommendations',
they're assuming responsibility for operational
characteristics of a system over which they
have no design authority or operational control.
I think it was last week that I posed the
question: "What is the imperative for knowing
oil pressure or engine rpm in the first
few seconds after engine start?" I'll
bet there's not a single instructor-pilot
who can articulate an answer based on
simple-ideas . . . but they will be glad
to pass along a legacy operational imperative
handed down from Charles Lindbergh.
Bob . . .
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
